Respond when someone likes or comments on your post. Visit their blog and send your comment love. Courtesy brings in more readers and friends.
Always let the picture do the talking! As a picture speaks a 1000 words.
Grammar - Depending on the language you use, blogging just makes it imperative that you are reasonably good with your grammar skills and proficiency if not a master. Remember your audience is a mix of both; the ones who are experts and the ones who are not.